Problem: A bag contains $4$ red marbles, $4$ green marbles, and $10$ blue marbles. If a marble is randomly chosen, what is the probability that it is blue?
Answer: There are $4 + 4 + 10 = 18$ marbles in the bag. There are $10$ blue marbles. The probability is $ \frac{10}{18} = \dfrac{5}{9}$.